1. Field of the Invention
The invention relates to refrigerators, and more particularly, to a system for delivering power to and transferring data to and from removable shelves in a refrigerator compartment.
2. Description of the Related Art
As used herein, the term xe2x80x9crefrigeratorxe2x80x9d denotes a cabinet that has an internal temperature lower than ambient, and includes what are commonly termed refrigerators and freezers, as well as combinations thereof.
Current refrigerators sometimes have more than one compartment, each having a different environmental parameter such as temperature. Thus, for example, a refrigerator may have a refrigeration compartment where temperature is maintained above 0xc2x0 C. and a freezer compartment where temperature is maintained below 0xc2x0 C. Control of the temperature in the refrigerator is generally provided from a single control circuit, with a single set of controls that are adjustable to a user. In some cases, a freezer compartment and a refrigeration compartment may have separate controls for each.
It is known that different foods are best preserved at different temperatures. For example, in refrigeration, colder temperatures are better for preserving meats, and less cold temperatures are better for preserving fruits and vegetables. Similarly, in a freezer compartment, colder temperatures are sometimes better for preserving certain foods than others. To accommodate these different needs, refrigerators are known to have drawers or spaces where slightly different temperatures or humidity levels can be achieved. For example, the refrigeration compartment may have separate drawers for vegetables and meat, each of which has slide controls to allow air circulation at selectable rates to permit slight adjustment of temperature or humidity levels within the drawers. U.S. Pat. No. 4,638,644 discloses removable, sealable shelves that enable a user to adjust the size and location of a compartment within a refrigerator. However, the temperature within the compartment so defined can only be controlled by manually adjusting baffles affecting the air flow within the refrigerator.
One problem with current systems is that there is a limit to the available temperature gradient between compartments. Refrigeration controls control the overall temperature of the refrigerator. Consequently the temperature of individual compartments within the refrigerator is necessarily tied to the overall temperature. The differences can only be accomplished by altering general airflow between compartments. Yet a higher temperature gradient may be desirable to best preserve certain foods.
Another problem is that the location of compartments often determines the available temperature range within the compartment. Generally, colder temperatures pertain at lower locations within a refrigerator. Thus a colder temperature at a higher location within a compartment may be unattainable with present systems.
Another problem is that controls are not always conveniently located. They may be blocked by items in the refrigerator, or located in a compartment remote from the space the user desires to control.
These and other problems are solved by the present invention where power is delivered to a removable shelf within a refrigerator compartment. More particularly, the refrigerator comprises one or more compartments and is selectively enclosable by a door. It also contains one or more removable shelves and means for mounting each removable shelf within the compartment. In accord with the invention, a power bus is disposed within the compartment, electrically connected to a power source, and a connector is disposed on the removable shelf. Thus, when the removable shelf is mounted within the compartment by the mounting means, the connecter is connected to the power bus to deliver power to the removable shelf. Preferably, the power bus comprises a ground conductor and a power conductor.
In one aspect of the invention, the refrigerator has a control circuit for controlling at least one atmospheric parameter within the compartment. A shelf portion of the control circuit is mounted to the removable shelf, and a main portion of the control circuit is disposed remotely of the removable shelf. The shelf circuit portion is powered by way of the power bus when the removable shelf is mounted within the compartment by the mounting means. Preferably, the parameter controlled by the control circuit is temperature, and the shelf circuit portion has a user interface for adjusting the temperature from the removable shelf. Thus, actuation of the user interface generates a data signal in the shelf circuit portion and the data signal is transmitted to the main circuit portion. The data signal is transmitted to the main circuit portion by way of the power bus, or by way of induction, or by way of at least one data line.
Ideally, the power source is an isolated power supply in the main circuit portion, preferably at 24 volts. The main circuit portion can have a constant current source and a voltage comparator coupled to a refrigerator control. Also, the constant current source can comprise a transistor. Preferably, the constant current source and the voltage comparator are connected to the refrigerator control by at least one opto-isolator.
In one embodiment, the shelf circuit portion comprises a first user interface circuit having a first switch, at least one LED and a first resistor, the first switch and the at least one LED being connected in series and the first resistor and the at least one LED being connected in parallel. In a first mode, the first switch is actuated and the at least one LED is lit, indicating a first user setting. Another aspect of this embodiment comprises a second user interface circuit having a second switch, at least one second LED, and a second resistor, the second switch and the at least one second LED being connected in series, and the second resistor and the at least one second LED being connected in parallel, the second resistor having a significantly different resistance value than the first resistor, the first user interface circuit and the second user interface circuit being connected in parallel.
In either case, the shelf circuit portion or the main circuit portion can have a capacitor connected in series across the power supply to the first and second resistors, so that selective actuation of the first or second switch will disengage the LED serially connected to the actuated switch, causing voltage to rise in the capacitor at a rate determined by the resistance value of the resistor serially connected to the actuated switch, which rate is timed by the voltage comparator and signaled to the refrigerator controller. Hence, the refrigerator controller can identify which switch is actuated.
In another embodiment, the shelf circuit portion comprises a touch sensor switch, a microprocessor, a voltage regulator, a capacitor, and at least two parameter circuits, each parameter circuit corresponding to a predetermined microenvirornment within the compartment, and each parameter circuit comprising an LED, an LED resistor and an LED drive transistor, serially connected. The parameter circuits, microprocessor, touch sensor switch are connected in parallel, and the main circuit portion has a microprocessor. Thus, actuation of the touch sensor switch for a selected setting sends a signal corresponding to the selected setting to the main circuit portion microprocessor by way of the power bus. Preferably, actuation of the touch sensor switch signals microprocessor 158 to disengage the LEDS for a set time value. Thus the selected setting can be received and stored by the main circuit microprocessor. Also, preferably, power to the shelf circuit portion is discontinued when the door is closed.
In a further aspect of the invention, the mounting means includes a shelf ladder and the removable shelf has a bracket that mounts to the shelf ladder to support at least a portion of the removable shelf by cantilever. Preferably, the power bus is within the shelf ladder.
In a further aspect of the invention, a microenvironment zone is partially defined by the removable shelf, and the removable shelf comprises a user interface that controls at least one atmospheric parameter within the microenvironment zone. Here, the refrigerator has a control circuit for controlling the at least one atmospheric parameter. The removable shelf comprises a shelf portion of the control circuit, and a main portion of the control circuit is disposed remotely of the removable shelf. Thus, the shelf circuit portion is powered by way of the power bus when the removable shelf is mounted within the compartment by the mounting means. Preferably, the power bus comprises a ground conductor and a power conductor, the power conductor comprising separate sections, one section for each microenvironment zone. And further, the refrigerator comprises visual indicia to indicate the location of each microenvironment zone.